Arrangements for fixing a sheet of transparent plastic material in an opening of an awning are well-known in the art. In most cases the sheet of transparent plastic material forms a window, e.g. in a tent awning or in a convertible canopy top.
It is a problem, particularly in convertible canopy tops, that the awning cloth is more durable and sturdier than the transparent plastic material used for the window-forming part of the convertible top, the window allowing the driver to monitor the traffic behind him. The fact that the awning cloth is still in an acceptable condition when the transparent plastic material, used for the rear window of a canopy top, is worn out is mainly caused by the sensitivity of the transparent plastic material to UV-radiation. UV-rays emitted by the sun cause aging of the plastic material which becomes brittle long before the canvas or other material used for the awning cloth loses its characteristic properties. A consequence is that the brittle plastic material cracks or ruptures under tensioning of the material when it is stretched by the rods or poles of the spanning construction of the convertible top.
Another reason that the rear window of a convertible top becomes worn out or blinded long before the canvas of the awning has to be replaced is that dust or sand causes scratches on the plastic material. The scratches interrupt and disperse light beams, thereby rendering the window blind (translucent or opaque) rather than transparent and clear, and thus hampering the rear view of the driver.